My son's build had a problem today -- the computer was sleeping, he heard a pop, came in and the power was out to the wall outlets. I flipped the breaker back on, but computer wouldn't start -- no power, nothing. I pulled the power unit, took it to Fry's, they plugged it in and got a loud pop and sparks. I bought another power supply, installed, computer now starts but having a weird issue with graphics card.

Windows 10, 64 bit

Intel i7-4790k

Gigabyte GA-Z97X

Sapphire Radeon R9 390X EVGA

SuperNOVA 850 G2 Power Supply - 80 PLUS Gold - 850W

Corsair 16GB DDR3 Vengeance Pro Series, 2400 MHz (two sticks)

He has the Radeon on his right-hand monitor, and the on-board video on his left monitor. His set up worked fine for the last several months, until today. When I boot up the computer, the BIOS and then Windows "churning" symbol displays, then the right monitor goes off and stays blank, and the left monitor displays Windows. I noticed when this happens, the fans on the Radeon power off. I cannot use an AMD driver without the card shutting off during boot up as described above.

I downloaded and ran DDU from Guru3D and rebooted (read to do that here), then the Radeon works fine. However, when I install the most recent AMD drivers (from their site), the graphics card again shuts off during boot up, as described above.

I figured since the graphics card worked after I ran DDU, then we'd go with that, but now performance has slowed to a crawl -- I am thinking maybe Windows has assigned a default basic driver to the card, and the RAM is not being utilized. Since then I have repeated using DDU and installed the 15.1 drivers, 16.1, etc until the most recent. Still not working. Windows installed it's own driver so card works but clearly not recognizing the 8gb.

I don't think anything else was damaged when the first power supply (an EVGA 1000) popped, but not sure.....it could be the graphics card or something else was damaged.

I am assuming going from the EVGA 1000 down to the EVGA 850 was not too large a drop in power, but please correct me if so (I read somewhere here that the Radeon R9 390X would run with a 350 power supply).

A "pop" or "I need to change my pants now"? Pops aren't good, they're usually delivery side (transformer circuitry to system) and more harmful to the components than the supply side (wall to transformer), where the failure sounds like a gunshot or small explosion. You need to try the card in another system, but I would bet it was damaged in the resulting 1800w surge, and is the most vulnerable component.

Also you should look into an 850w UPS, if a power supply goes it will trip the current protection in it before doing real damage.

Thank you! I will try to get the card out and get it working in another computer. I am not sure at all about the mobo, nor the gpu. Can you or anyone recommend software or something I can test it with?